Process for the manufacture of filaments of poly-beta-methyl-beta-butyrolactam



the limits of 1:12 to 1:1.9.

United States Patent ,49 6 Claims. (Cl. 264-203) The present inventionrelates to a process for the manufacture of filaments ofpoly-fi-methyl-fibutyrolactam.

For the manufacture of spinning solutions capable of being readilyfiltered it has been proposed in US. patent application SN. 198,446,filed on May 29, 1962, now Patent No. 3,231,539, in the name of HansHoyer et al., for Process for the Manufacture of Spinning Solutions ofPolyamides to dissolve poly-B-lactams, especiallypoly-fi-methyl-[i-butyrolactam, in a methanolic solution of calciumthiocyanate.

In order to achieve that the aforesaid polymer dissolves readily, theconcentration of the spinning solution of calcium thiocyanate shouldpreferably be 23 to 26 percent by weight, in which case the proportionby weight of polymer to (anhydrous) calcium thiocyanate can vary withinThe calcium thiocyanate is generally used with 4 moles of water so thatthe spinning solutions generally contain 9 to 11 percent of water. Thewater content of the solvent methyl alcohol/ calcium thiocyanate shouldnot exceed 13 percent because otherwise the solvent would not dissolvethe polymer to a sufiicient extent.

The very high salt content of the spinning solution of about 23 to 26percent by weight promotes sticking of the capillary filaments of thefreshly spun filament after leaving the precipitating bath, above allduring the drawing process which follows immediately. The textileusefulness of such sticky filaments is, of course, substantiallyimpaired so that they cannot be processed at all or with greatdifficulties only.

Now I have found that sticking of the capillary filaments can be avoidedby spinning a methanolic solution, which contains 19.5 to 18 percent byweight of poly-B- methyl-fi-butyrolactam, 19 to 25 percent by weight ofcalcium thiocyanate and 9 to 11 percent by weight of water, thepercentages by weight being calculated on the total solution, intodesalted water having a temperature Within the range of from 11 to 25C., drawing the coagulated filaments, after they have left the water, to6 to 11 times their original length, drying them with simultaneouslongitudinal shrinkage by 3 to percent and subjecting them to a hotwater fixation at a temperature within the range of from 68 to 160 C.

Thus the composition of the spinning solutions may vary to aconsiderable extent. Their viscosity should lie within the range of from40 to 800 seconds at C. (measured by the falling ball test with a steelball having a diameter of 3 mm). The viscosity of the spinning solutiondepends, in addition to its composition, essentially also on theinternal viscosity of the polymer used. The relative viscosity of thepolymers used can vary Within the range of from 7.5 to 34, measured as asolution of 1 percent strength by weight in sulfuric acid of 96 percentstrength by weight at 20 C.

The calcium thiocyanate is preferably used as a salt containing crystalwater with 4 moles of water per mole of calcium thiocyanate. The desiredwater content is easily attained with this salt.

The water which is used as precipitating bath may not "ice containsulfate ions or carbonate ions because these ions would form difiicultlysoluble salts with the calcium ion of the spinning solution. Thepresence of small amounts of chlorides, for example potassiumor sodiumchloride, or nitrates does not disturb the spinning process. On thecontrary, these salts contribute towards diminishing the stickingtendency of the single filaments of the filament bundle. Since even withthe use of boiler feed water owing to the low content of alkalibicarbonatesdeposits of calcium carbonate at the Walls of the containerused for the coagulation bath and at the nozzles cannot be avoided, itis necessary to use distilled water or desalted Water for thepreparation of the coagulation bath.

The temperature of the precipitating bath must be maintained within thelimits indicated above. At a temperature exceeding 19 C., filaments areobtained which have a pronounced tendency of stick and are, therefore,entirely useless. At a temperature of the precipitating bath of below 12C., filaments are obtained which do not stick but which cannot be drawnto a sufiicient extent and whose ultimate tensile strength is entirelyinsufficient. The temperature constant of the precipitating bath canalso be of importance. Especially with the use of polymers of low andmedium relative viscosities of 7 to 11 (measured as a solution of 1percent by weight in sulfuric acid of 96 to 97 percent by weight), thereare obtained, depending on the composition of the spinning solution usedin each case, filaments which do not stick only in case the chosenspinning temperature is maintained at :*:1.5 C.

The preferred temperature of the spinning bath depends on severalfactors:

The admissible temperature range of the precipitating bath, within whichfibers are obtained that do not stick, is the broader the higher therelative viscosity of the polymer and the more uniform the structure ofthe polymer.

The chosen temperature of the spinning bath is the higher the lesscalcium thiocyanate is used in proportion to the polymer.

Spinning solutions with a veryhi h falling ball viscosity are generallyspun at a temperature of the precipitating bath of from 20 to C., inparticular in those cases in which simultaneously a polymer of a highrelative viscosity is used.

The temperatures of the spinning bath should be the lower the higher theindividual titer of the filament.

Calcium thiocyanate and methyl alcohol are of necesstiy entrained intothe precipitating bath due to the precipitating process. The coagulationbath should advantageously flow countercurrently to the drawingdirection of the spinning filament in order that the filament leaves thecoagulation bath in as salt-free a state as possible. The coagulatedbundle of filaments is drawn off through the spinning bath at a rate of1 to 6 m./min.

On leaving the spinning bath, the filaments are drawn on trio rollers to6 to 11 times their original length. The drawing of the still moistfilaments can take place in air or in a water bath. The temperaturesduring the drawing process can vary within wide limits up to thetemperature of boiling water. However, the best strength values areobtained when the filaments are drawn at temperatures within the rangeof from 15 to 25 C.

To ensure a good quality of the filaments, it is important that duringthe first drying process a shrinkage of about 3% to 15% sets in. Dryingon so-called shrinkage spools is preferred, with an admitted shrinkageof 7 to 10%.

After the first drying-shrinking process, the filaments still have aboil shrinkage of to 64% on an average. To eliminate this boilshrinkage, the filament is still subjected to a hot water fixation attemperatures within a the range of from 68 to 100 C. The hot waterfixation can take place while maintaining the length of the filament orwhile drawing the filament. Drawing degrees of from 5 to of the originallength are preferred. Owing to this heat treatment, the crystallinestructure of the filament is rearranged while the high boil shrinkage ofthe filament, which has been freshly spun, drawn and dried withsimultaneous shrinkage, is substantially reduced. It is especiallyadvantageous to carry out the hot water fixation in two stages with anintermediate drying whereby the boil shrinkage is first reduced to 5 to20% by an initial hot water fixation and, after an intermediate drying,the boil shrinkage of the filament is finally reduced to a value below 1percent by renewed fixation of the filaments with boiling water.

The application of the process according to the invention has, inaddition to the fact that sticking of the capillary filaments iseliminated, still other advantages. The filaments obtained are swollento a small extent. The spinning/swelling value is the lower the lowerthe temperature of the spinning bath within the range applied accordingto the invention. Under these spinning conditions the highest values ofultimate tensile strength and elongation are simultaneously obtained.The swelling value (i.e. the amount of water which is squeezed off) ofthe freshly spun and drawn filaments lies within the range of from 80 to140 percent before the first drying. It is reduced to- 40 to 50 percentafter the first drying. By the hot water fixation according to theprocess of the invention the swelling value is reduced to 20 to 30percent.

The following examples serve to illustrate the invention but they arenot intended to limit it thereto, the percentages being by weight:

Example 1 A solution of poly-[i-rnethyl-fl-butyrolactam with a viscositynumber according to Staudinger of 5.1 (c.f., for example, UllmannEncyclopadie der technischen Chemie, vol. 211, page 779), whichcorresponds to a relative viscosity of 16.4 (determined as a solution of1% strength by weight in sulfuric acid of 96% by weight at 20 C.) inmethanolic calcium thiocyanate having a composition of 13.9% polymer,22.3% calcium thiocyanate, 10.4% water (the calcium thiocyanate containsabout 4 moles crystal water) and 53.4% methyl alcohol, was spun by meansof a tantalum nozzle having 30 bores of a diameter of 0.07 mm. each intodistilled water or into water that had been completely desalted by meansof an exchanger. The viscosity of the spinning solution was 126 secondsat 20 C. (according to the falling ball test carried out with a steelball of a diameter of 3 mm.). The distance of the spinning bath was 165cm. and the spinning solution was forced into the coagulation bath at arate of 0.95 g./min., which corresponds to a spinning rate of 8.2m./min. The spinning rate was computed from the number of -bores=n, theradius of the nozzle orifice=r, the weight of the solution conveyed perminute=V and the length of the computed cylinder or the desired spinningrate=h according to the formula T 1r-TL-lL=V; h= T 1r-77,

The temperature of the coagulation bath was maintained at 17.5 C. bymeans of a thermostat. The filament leaving the spinning bath at a rateof 2.5 m./min., which was squeezed ofi but was still moist (residencetime in the spinning bath about 39 seconds), was then drawn between twotrio rollers to 8 times its length in water having a temperature of 20C. The drawn filament was passed through wash water by means of twodrawing trio rollers at a rate of 20 m./min. without further drawing, tocompletely remove possibly adhering traces of calcium thiocyanate. Thenthe filament was passed under low tension at a drawing rate of 20.5m./min. through a preparation bath consisting of 4 g./l. of a reactionproduct of coconut oil amine +20 moles of ethylene oxide, and was woundwithout tension on a shrinkage spool turning at a rate of 20 m./min.During the subsequent drying process on a shrinkage spool, the filamentwas allowed to shrink by 7 to 10%. The dried filament still had a boilshrinkage of It was, therefore, subjected to a fixing process in hotwater of a temperature of, for example, 72 C. or 81 C. The higher thefixing temperature, the lower the residual shrinkage of the finishedfilament. At 72 C. the residual shrinkage amounted, for example, to 20%,at a fixing temperature of 81 C. it amounted to only 6%. When thefixation was carried out with boiling water, the residual shrinkage onlyamounted to 0.5 to 1%. The filament was interduced into the fixing bathgenerally by means of a trio roller at a rate of 18 m./min. and wasdrawn off from the fixing bath by another trio roller at a rate of 20m./min. Thus a slight drawing took place in the fixing bath.

The ultimate tensile strength of the filament was 295 g./100 den. at anelongation of break of 26%. The individual titer of a single filamentwas 2 deniers, while the total titer of the bundle was deniers.

By fixing the filament subsequently in boiling water, the boil shrinkagecould be reduced to 0.5 to 1%.

Example 2 A solution of poly-fi-methyl-B-butyrolactam with a viscositynumber according to S-taudinger of 3.1, which corresponds to a relativeviscosity of 7.5 (measured as a solution of 1% strength by weight insulfuric acid of 96% strength by weight at 20 C.) in methanolic calciumthiocyanate having a composition of 17% polymer, 23.2% calciumthiocyanate, 11.2% water and 48.6% methyl alcohol, was spun intodistilled water by means of a tantalum nozzle having 60 bores of adiameter of 0.07 mm. each, as described in Example 1. The viscosity ofthe spinning solution, determined according to the falling ball test,was 110 seconds at 20 C. (diameter of the steel ball: 3 mm.). Thespinning solution was forced into the coagulation bath at a rate of 1.18g./min. which corresponds to a spinning rate of 5.1 m./min. Thetemperature of the spinning bath was 16 C. The filament was processed asdescribed in Example 1.

The ultimate tensile strength of the filament was 290 g./ den. at anelongation of 25.7%. The individual titer was 1.6 den., the total titerof the strand was 95.5 den.

Example 3 A solution of poly-fi=methyl-,B-butyrolactam with a viscositynumber according to Staudinger of 5.1, which cor responds to a relativeviscosity of 16.4 (measured as a solution of 1% strength by weight insulfuric acid of 96% strength by weight at 20 C.) in methanolic calciumthiocyanate having the composition of 13.8% polymer, 22.3% calciumthiocyanate (anhydrous), 10.5% water and 53.4% methyl alcohol, was spuninto distilled water by means of a tantalum nozzle having 60 bores of adiameter of 0.07 mm. each, as described in Example 1.

The viscosity of the spinning solution, determined according to thefalling bal'l test, was 122 seconds at 20 C. (diameter of the steelball: 3 mm.). The spinning solution was forced into the coagulation bathat a rate of 2.54 g./min. which corresponds to a spinning rate of 10.8ITL/mll'l. The temperature of the spinning bath was 14.5 C. The filamentleaving the spinning bath at a rate of 2.5 rm/min. was drawn in waterhaving a temperature of 20 C. to 7 times its length, washed with waterand wound on a shrinkage spool at a rate of 17.5 m./min., the filamentbeing allowed to shrink by 7%. After drying at 35 C., the filament wasfixed in water having a temperature of 82 C. The filament obtained had aboil shrinkage of 15%. The individual titer of the filament was 3.0 den.It had an ultimate tensile strength of 240 g./100 den. and an elongationat break of 40%.

I claim:

1. A process for the manufacture of filaments of polyfi-methyl-fibutyrolactam, which comprises spinning a methanolic solution whichcontains 10.5 to 18 percent by weight ofpoly-flamethyl-fl-bu'tyrolactam, 19 to 25 percent by weight of calciumthiocyanate and 9 to 11 percent by weight of water, the percentages byweight being calculated on the total solution, into desalted waterhaving a temperature within the range of from 11 to 25 C., drawing thecoagulated filaments after they have left the water to 6 to 11 timestheir original length, drying them with simultaneous shrinkage by 3% to15% of their length and subjecting them to a hot water fixation withinthe range of from 68 to 100 C.

2. The process as claimed in claim 1, wherein the coagulated filamentsare drawn in a water bath having a temperature of 15 to 25 C.

3. The process as claimed in claim 1, wherein the coagulated and drawnfilaments are caused to shrink on a shrinkage pool by 7% to 10% of theirlength.

4. The process as claimed in claim 1, wherein the hot water fixation iscarried out in such a manner that the length of the filament ispreserved. 1

5. The process as claimed in claim 1, wherein the filaments aresubjected during the hot water fixation to a drawing of from 5% to 20%.

6. The process as claimed in claim 1, wherein the hot water fixation iscarried out in two stages by using first a water bath having atemperature of from 68 to 82 C. and then another water bath with boilingwater and drying the filaments between the two baths.

No references cited.

ALFRED L. LEAVITT, Primary Examiner.

1. A PROCESS FOR THE MANUFACTURE OF FILAMENTS OFPOLYB-METHYL-B-BUTYROLACTAM, WHICH COMPRISES SPINNING A METHANOLICSOLUTION WHICH CONTAINS 10.5 TO 18 PERCENT BY WEIGHT OFPOLY-B-METHYL-B-BUTYROLACTAM, 19 TO 25 PERCENT BY WEIGHT OF CALCIUMTHIOCYANATE AND 9 TO 11 PERCENT BY WEIGHT OF WATER, THE PERCENTAGES BYWEIGHT BEING CALCULATED ON THE TOTAL SOLUTION, INTO DESALTED WATERHAVING A TEMPERATURE WITHIN THE RANGE OF FROM 11* TO 25*C., DRAWING THECOAGULATED FILAMENTS AFTER THEY HAVE LEFT THE WATER TO 6 TO 11 TIMESTHEIR ORIGINAL LENGTH, DRYING THEM WITH SIMULTANEOUS SHRINKAGE BY 3% TO15% OF THEIR LENGTH AND SUBJECTING THEM TO A HOT WATER FIXATION WITHINTHE RANGE OF FROM 68* TO 100*C.